# LeetCode题解：(114) Flatten Binary Tree to Linked List

## 题目说明

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

     1

    / \
2   5
/ \   \
3   4   6


The flattened tree should look like:

  1

    \
2
\
3
\
4
\
5
\
6


## 题目分析

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
void flatten(TreeNode* root, TreeNode** &rightRef) {
if (!root) return;
*rightRef = root; // put root to right
TreeNode* right = root->right; // store right ptr
rightRef = &root->right; // move rightRef
flatten(root->left, rightRef); // link left to right
flatten(right, rightRef); // link right to the tail of left
root->left = nullptr; // null left
}

void flatten(TreeNode* root) {
TreeNode** right = &root;
flatten(root, right);
}
};


void flatten(TreeNode *root) {
while (root) {
if (root->left && root->right) {
TreeNode* t = root->left;
while (t->right)
t = t->right;
t->right = root->right;
}

if(root->left)
root->right = root->left;
root->left = NULL;
root = root->right;
}
}


（LeetCode评测时间也不是这么靠谱的，试着提交了给出的8ms样例，结果还是12ms XD）

posted @ 2018-04-03 19:58  森高Slontia  阅读(144)  评论(0编辑  收藏  举报